1.Continued studies of mutant mouse which stores cystine in lysosomes as do cystinotic patients; anamolies in cholesterol metabolism uncovered in Niemann-Pick C cells which show lysosomal storage of cholesterol and lack of intracellular cholesterol esterification. Investigation of effects of various cystine lowering drugs on levels of stored cystine in the mouse organs since there has not previously been an animal model for cystinosis. 2.Continued studies of cholesterol metabolism and transport in Niemann-Pick C and cystinotic fibroblasts. Investigation of the movement of cholesterol from the lysosomal compartment (where it is stored in Niemann-Pick C disease and in the mutant mouse) to the microsomes where cholesterol can be esterified and packaged for storage in lipid vesicles. 3.Characterization of cystinotic cell protein associated with cystine and present in a 2-fold excess in cystinotic versus normal fibroblasts. Amino acid analysis of this protein, Nterminal sequencing and a search for similar proteins. Since this protein has no covalently bound cystine, investigation of its cystine binding characteristics will be initiated. Findings will be compared with the known binding properties of the cystine binding protein from E. coli used in our laboratory to measure cystine levels in cystinotic cells. 4.Investigation of alternative ways of depleting cystine levels in cystinotic fibroblasts, using single and combined drugs that influence cystine levels in cystinotic fibroblasts. 5.Investigation of metabolism of ascorbic acid in normal and cystinotic fibroblasts. Continuation of measuring the kinetics of uptake of ascorbic acid by normal and cystinotic fibroblasts, followed by study of the effects this uptake has on the production of type I collagen, a major product of skin fibroblasts.